Field of the Invention
The present invention generally relates to a device for releasably locking an axially movable rod member.
Description of the Related Art
FIG. 1 shows a suction device that is adapted to a conventional vacuum transfer system. The suction device 10 includes a plurality of level compensators 13 connected to a vacuum chamber 11, wherein the level compensator 13 includes a pipe-type rod member 14, one end of which is inserted into a connection part 12, a suction pad 15 coupled to the other end of the rod member 14, and a spring 16 coaxially disposed around the rod member 14 and connected between the connection part 12 and the suction pad 15.
In this configuration, the rod member 14 is axially movable so that respective suction pads 15 can be brought into close contact with the surface of an object P in a high degree even when the surface is generally uneven. However, there is a problem in that the rod member 14 is still in a movable state when the object has been lifted. Accordingly, in this situation, a device for locking the rod member 14 is required.
For example, FIG. 2 shows an air-locking device for a rod member that is disclosed in Korean Patent No. 10-0883882. The device 20 is a device that uses a so called chuck structure as a locking means. Here, the chuck structure 21 includes a cylinder body 22 inserted around a rod member 27 and a plurality of jaws 23 disposed upwards from the cylinder body 22. The chuck structure is configured such that as the cylinder body 22 slides along the rod member with the actuation of a piston 25 or a spring 24, which is provided below the cylinder body 22, the jaws 23 lock the rod member 27 with the compression by an inner wall of a housing 26 surrounding the jaws.
The locking device 20 is useful in an aspect of enabling the rod member 27 to be locked and unlocked. However, it also has problems primarily in that: due to its sliding mechanism,
(1) there is severe friction and abrasion among surface-contacted locking elements, i.e. among housing 26-chuck structure 21-rod member 27,
(2) accordingly, smooth locking of the rod member 27 cannot be obtained, and the like.
As another example, FIG. 3 shows a lock mechanism disclosed in U.S. Pat. No. 6,178,870. This mechanism 30 is a so called wedge-type mechanism that includes: in an internal space of a housing 32 surrounding a rod member 31,
a reciprocating piston 33;
a ball 35-retainer 36 supported by an inner spring 34 on one side of the piston 33;
an inclined ring 37 coaxially disposed around the retainer 36 and supported by one side of the piston 33 via contact therewith; and
an outer spring 38 coaxially disposed around the inclined ring 37 while coming into contact with an inner wall of a housing 32 surrounding the outer spring, thereby elastically supporting the movement of the inclined ring 37 by the piston 33.
This mechanism 30 may solve the problems of the above-mentioned sliding-type locking device in that the rod member 31 is locked by the compression of the ball 35 by a wedge member 36 and 37. However, this mechanism also has problems in that it has a complicated structure, so proper arrangement and assembly of respective elements are difficult.
That is, in order to configure the mechanism 30, locking elements, i.e. the retainer 36, the inner spring 34, the inclined ring 37, and the outer spring 38 should be sequentially arranged and assembled in position about the piston 33. However, the mechanism has problems as follows:
(1) the configuration is complicated;
(2) it is very difficult even for a skilled person to accurately and quickly assemble the respective elements 33 to 38 within a defined space of the housing 32; and
(3) even upon disassembly, treatment of respective elements 33 to 38 is very troublesome and inconvenient.
Further, in the mechanism 30, the retainer 36 should be moved within a predetermined range for locking or unlocking of the rod member 31. However, this motion is obtained by the following configurations:
that the retainer 36 and the inclined ring 37 are respectively assembled based on the piston 33;
that the retainer 36 is separately supported by the inner spring 34;
that an inner surface of the inclined ring 37 is inclined; and
that the outer spring 38 supporting the inclined ring 37 is disposed around the inclined ring 37 and supported by the inner wall of the housing 32 via contact therewith.
Thus, locking operation is not stably performed due to such complicated configurations.
The foregoing is intended merely to aid in the understanding of the background of the present invention, and is not intended to mean that the present invention falls within the purview of the related art that is already known to those skilled in the art.